The present paper addresses the positive human rights obligations of a hiring state with respect to violations of human rights by Private Military or Security Companies (PMSCs / contractors) that it employs, which arise from the obligation to prevent such violations, as well as the obligations to legislate, investigate, and prosecute and punish. The contribution is limited to scenarios where PMSCs provide coercive services in a theatre of conflict. Examples include combat, guarding and protection of persons or property, or detention and interrogation. The analysis demonstrates that hiring states have numerous positive obligations under Human Rights Law that can be highly relevant to PMSC operations in situations of conflict, including duties to oversee, control, and where necessary physically prevent conduct likely to threaten the right to life or the prohibition of torture and cruel and inhuman treatment. Where violations have already occurred or have been alleged, the duty to investigate, prosecute and punish obligates states to provide for a structure facilitating the reporting of such allegations, to quickly and effectively follow up on them and to ensure that they are properly processed through the system of justice. These provisions can, for the most part, be extended to conduct of third persons and thus also to contractors providing coercive services, even where their conduct may not be attributable to the state.